ORIGINAL: DavidAgar
A police radar gun works well. A mathmatician with a stop watch and you flying in between 2 fixed points will work or you can do what I do, take a stab in the dark and say 30 MPH. Good Luck, Dave
[link=http://www.amazon.com/Mattel-J2358-Hot-Wheels-Radar/dp/B000EHLB0M]Hot Wheels Radar Gun[/link]
$26.95
Ken